According to the International Energy Outlook 2006, Report No. DOE/EIA-0484 (2006) from the U.S. Dept. of Energy, the world's total net electricity consumption is expected to more than double during the period 2003-2030. Much of the electricity is expected to be used to provide commercial and residential lighting. Adoption of energy-efficient technologies can help to conserve electricity thereby slowing the growth in both the “peak demand” and “base demand” components of electricity demand. Base demand is the steady-state, or average, demand for electricity, while peak demand occurs when the demand for electricity is the greatest, for example, during a hot summer day when electricity use for air conditioning is very high. Reducing either type of demand is desirable, but a reduction in peak demand generally is more valuable because of the relatively high unit cost of the capacity required to provide the peak demand.
One way to conserve energy is to replace existing light fixtures that use older, less-efficient lighting technologies with light fixtures that use newer, more efficient lighting technologies. For example, highly efficient compact fluorescent light fixtures are commonly used to replace less-efficient incandescent lamps in existing household fixtures. To further reduce electricity demand, one or more light pipes may be incorporated into a wall or roof of a building. A light pipe distributes natural light from the sun or moon into an interior space. What is needed is a method and a system for controlling artificial lighting based on an amount of light distributed from a natural lighting system such as a light pipe. What is further needed is a method and a system for controlling artificial lighting in a manner that can function with acceptable reliability over large distances, in the presence of obstructions, and when subjected to intermittent electromagnetic noise.